1. Field of the Invention
This invention relates to an improved adhesive composition. The composition is comprised of a thermoplastic adhesive resin particularly a polymeric fat acid polyamide having small amounts of a bisphenol added as an adhesion promoter. The combination provides improved adhesion to various plastic substrates and a lower viscosity which facilitates application of the resin to substrates.
2. Description of the Related Art
Hydroxyl substituted aromatic compounds including bisphenols have been used in the past with various thermoplastic polymers for a variety of purposes. There they have been employed as light, heat and air stabilizers and as a plasticizer.
In U.S. Pat. No. 3,454,412 among heat, light and air stabilizers for polymeric fat acid polyamides are included alkylated bisphenols such as 4,4'-thiobis(6-tert-butyl-o-cresol) 2,2'-thiobis(4-methyl-6-tert-ketyl)phenol, and 2,6-bis(2.pi.hydroxy-3'-tert-butyl-5'-methyl benzyl)-4-methyl phenol. The compounds are employed in amounts of from 0.5% up to 2%.
In CA 68:30684 reference is made to a French Pat. No. 1475376 in which .alpha.-naphtol is employed with a polyamide of fatty acid dimers as an adhesive for plasticized polyvinyl chloride.
In CA 73:36447 reference is made to Japan No. 70 05 400 in which Bisphenol A is included along with octyl p-hydroxybenzoate in a nylon 6 and nylon 6,6 adhesive for cloth. In CA 79:63376 reference is made to Japan Kokai No. 73 36249 which utilizes Bisphenol A to stabilize polyamide solution.
At CA 83:60572 reference is made to Japan Kokai No. 73 47551 in which bisphenols are employed as polyamide plasticizers.